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.Dd August 24, 2000
.Dt I386_SET_WATCH 3
.Os
.Sh NAME
.Nm i386_clr_watch ,
.Nm i386_set_watch
.Nd manage i386 debug register values
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In machine/reg.h
.In machine/sysarch.h
.Ft int
.Fn i386_clr_watch "int watchnum" "struct dbreg *d"
.Ft int
.Fn i386_set_watch "int watchnum" "unsigned int watchaddr" "int size" "int access" "struct dbreg *d"
.Sh DESCRIPTION
The
.Fn i386_clr_watch
function
will disable the indicated watch point within the specified debug
register set.
.Pp
The
.Fn i386_set_watch
function
will set up the specified debug registers as indicated by the
arguments.
The
.Fa watchnum
argument specifies which watch register is used, 0, 1, 2, 3, or \-1.
If
.Fa watchnum
is \-1, a free watch register is found and used.
If there are no free
watch registers, an error code of \-1 is returned.
The
.Fa watchaddr
argument
specifies the watch address,
.Fa size
specifies the size in bytes of the area to be watched (1, 2, or 4 bytes),
and
.Fa access
specifies the type of watch point:
.Pp
.Bd -literal -offset indent -compact
DBREG_DR7_EXEC	  An execution breakpoint.
DBREG_DR7_WRONLY  Break only when the watch area is written to.
DBREG_DR7_RDWR	  Break when the watch area is read from or written
                  to.
.Ed
.Pp
Note that these functions do not actually set or clear breakpoints;
they manipulate the indicated debug register set.
You must use
.Xr ptrace 2
to retrieve and install the debug register values for a process.
.Sh RETURN VALUES
On success, the
.Fn i386_clr_watch
function returns 0.
On error, \-1 returned which indicates that
.Fa watchnum
is invalid (not in the range of 0-3).
If the specified watchnum was already disabled, no error is returned.
.Pp
On success, the
.Fn i386_set_watch
function returns the
.Fa watchnum
argument, or the watchnum actually used in the case where the specified
.Fa watchnum
was \-1.
On error, the
.Fn i386_set_watch
function returns \-1 indicating that the watchpoint could not established
because either no more watchpoints are available, or
.Fa watchnum ,
.Fa size ,
or
.Fa access
is invalid.
.Sh SEE ALSO
.Xr ptrace 2 ,
.Xr procfs 4
.Sh AUTHORS
This man page was written by
.An Brian S. Dean .
